1. Field of the Invention
The present invention concerns electronic systems in general, and particularly electronic systems realized in the form of Integrated Circuits (“IC”), integrated in two or more chips.
2. Discussion of the Related Art
“Multi-Chip Modules” or MCM, also known as SIP (“System-in-Package”, i.e. electronic systems contained in a single package) are known in the art, that include two or more ICs, constituting respective sub-systems of the electronic system, integrated in respective chips and contained in a single package.
The SIPs are often used in alternative to systems denominated SOCs, (“System-On-Chip”, i.e. whole electronic systems integrated on a single chip), in which all the circuital parts that compose of the electronic system to be realized are integrated in a single chip.
In an SOC, the IC integrated in the single chip can for instance include a microcontroller or a microprocessor, and/or a Digital Signals Processor (DSP), a memory constituted by one or more memory blocks of various type, such as for example Read Only Memories (ROM), Random Access Memories (RAM), and non-volatile memories, for instance of Flash type, to store the program that is to be executed, for example, by the microcontroller that governs the operation of the SOC, as well as blocks of management of the power supply (like, for instance, voltage regulators and charge pumps) and all the circuits that enable the communication of the IC with the outside.
Various types of SOCs are available in commerce, such as custom-designed (“full custom”) SOCs or SOCs with programmable functionality, programmable by an external user (like for instance in the case of “Field Programmable Gate Arrays”, FPGAs). In any case, the SOCs are normally realized by integrating the circuit components on the single chip using a single, very complex manufacturing process flow, because it has to include all the phases necessary to the realization of components very different from one another.
The complexity of the manufacturing process constitutes a disadvantage of the SOCs, that has a significant impact in terms of achievable yield in manufacturing process. Additionally, the SOCs of “full custom” type exhibit a high cost of development, which substantially impacts on the total production costs of the implemented electronic system.
The SIPs do not exhibit the above-mentioned drawbacks, since, as mentioned, they comprise two or more chips, in each of which a respective IC is integrated, by means of an ad-hoc manufacturing process, adapted in use to perform its own function, independently from that of the ICs integrated in the other chips contained in the same package. For instance, in a chip the microcontroller or the microprocessor or the DSP is integrated, in another chip the RAM is integrated, in still another chip the ROM or the Flash memory is integrated.
In a SIP, every IC includes a functional circuit core adapted to implement the specific functionality required to that IC, but a high number of service circuit structures is also integrated in every chip, that interact with the functional circuit core.
For example, in the case of a microcontroller, the functional circuit core is constituted by the central processing unit (the so-called CPU), in the case of a memory device, the functional circuit core includes a memory cells matrix; still in the case of a memory, the service circuit structures include all the circuit components adapted to manage the operations to be performed by the memory device, typically data read operations and, where the memory is programmable, data write and erase operations; typically the service structures include for example the charge pumps adapted to generate the operational voltages used during the write/erase operations on the memory, the decoding circuits for accessing the memory cells and the input and output buffers used for interfacing the chip with the external environment. In the case the IC is a microcontroller, the service circuit structures also include the input/output buffers.
The Applicant has observed that the integration, on every chip, of the service circuit structures, is disadvantageous in general, since it leads to an increase in area of material, and this is particularly true in systems to be used in portable apparatuses (like, for instance, in MP3 devices and in cellular phones), in which it is important to reduce the space occupation.
Additionally, it often happens that the service circuit structures are designed to satisfy less stringent requirements compared to those required to the functional circuit cores of the ICs. In other words, the service circuit structures are realized with design rules and manufacturing process different from, being more relaxed, those related to the functional cores; integrating on a same chip both the functional cores and the service circuit structures of the ICs has the result that the lithographic apparatuses used during the production process are not exploited at the best of their possibilities: often in fact in an IC a 50% thereof is represented by the service circuit structures.